1. Field of the Invention
The present general inventive concept relates to a pickup device used with an image forming apparatus, and more particularly, to a pickup device used with an image forming apparatus, which does not overload a driving motor even if a paper pickup roller is overloaded.
2. Description of the Related Art
FIG. 1 is a side cross-sectional view showing a conventional pickup device in an image forming apparatus, to illustrate a paper pickup motion, and FIG. 2 is a side cross-sectional view showing the conventional pickup device of FIG. 1, to illustrate an overloaded state when the conventional pickup device is not able to pickup paper.
Referring to FIG. 1, a paper supporter 11 is mounted on a cassette 10 and a spring 12 elastically supports the paper supporter 11. Sheets of paper S are piled on the paper supporter 11.
A pickup device 20 is placed on the upper portion of the cassette 10 to pickup the sheets of paper S one by one. The pickup device 20 is placed on an axle 22 so that the pickup device 20 can rotate with respect to the axle 22. The pickup device 20 includes a driving roller 21 that receives a driving force from a driving motor (not shown), a pickup roller 24 that is in contact with the sheets of paper S and picks up the sheets of paper S, and a plurality of idle rollers 23 that connect the driving roller 21 and the pickup roller 24 and send the driving force of the driving roller 21 to the pickup roller 24.
The pickup device 20 pivots in a direction of an arrow “A” with respect to an axis of the axle 22. To pickup the sheets of paper S, the pickup device 20 moves from a position indicated by a dotted line toward the sheets of paper S. Then, the pickup roller 24 comes in contact with one sheet of paper S, picks up the sheets of paper S one by one by a friction with the sheets of paper S, and feeds the sheets of paper S into a main body of the image forming apparatus.
Recently, as different types of paper are used, a friction between a sheet of paper and a pickup roller differs according to each type of paper. That is, some sheets of paper have a smoother surface than ordinary sheets of paper to allow a clearer development of an image and some sheets of paper have different finishing on each side of the paper, which makes it difficult for a pickup roller to pickup the paper because the friction between the pickup roller and the paper varies according to the different finishing on each side of the paper.
Referring to FIGS. 1 and 2, the pickup device 20 moves with the axle 22, and the pickup roller 24 comes in contact with the sheets of paper S and rotates. However, the pickup roller 24 cannot pickup the sheets of paper S. In this case, the pickup device 20 moves further towards the sheets of paper S with respect to the axle 22 and applies a higher vertical force in a direction of an arrow “B” to increase a friction with the sheets of paper S.
As such, the pickup roller 24 is overloaded and the overload is passed on to the idle roller 23, the driving roller 21, and finally to the driving motor (not shown), thereby damaging the driving motor.